These studies are directed toward evaluation of the prognostic power of the electrocardiogram when analyzed by advanced computer methodology and the predictive accuracy of diagnostic criteria when implemented in ECG computer programs. Digital signal processing of the electrocardiogram is a problem area requiring considerable engineering and computer science expertise as well as knowledge about its clinical relevance. The use of well-documented populations and multivariate statistical techniques in designing new criteria are also subjects under investigation. Studies have been pursued in collaboration with NHLBI and the Framingham Heart Study. The Framingham Heart Study has shown that left ventricular hypertrophy (LVH) is an independent risk factor for pathological cardiac events; an important screening modality for LVH is the routine, diagnostic electrocardiogram since more the 100 million are performed annually in the U.S. Collaborative studies show that when age and indices of body habitus, stratified by sex, are combined with ECG parameters, the sensitivity and specificity of LVH diagnoses are significantly improved, which would result in more and earlier diagnoses. Another important diagnostic modality is the ambulatory electrocardiogram (AECG), which by virtue of collecting hours to okays data has much greater potential for evaluation of symptoms that may be caused by cardiac arrhythmias or myocardial ischemia as well as a tool for detecting alterations in cardiac electrophysiology that may have prognostic significance. Studies of the methodology for analyzing AECGs are being pursued in collaboration with NHLBI.